(1) Field of the Invention
The present invention relates to a flush toilet bowl, and more particularly to a toilet bowl of the type in which water is supplied by gravity and sewage is discharged by a siphoning action.
(2) Background
In response to the need to conserve water, governments everywhere have looked for ways to reduce the amount of water used by the customers of municipal water companies. Toilets have long been identified as major users of water. It is not surprising therefore that many municipal programs and new laws have focused on reducing water used by toilets.
Before the 1950s, toilets typically used 7 gallons or more for each flush. By the end of the 1960s, toilets were designed to flush with only 5.5 gallons, and in the 1980s the new toilets being installed were using only 3.5 gallons. Beginning in the 1980's some states passed laws requiring that toilets use no more than 1.6 gallons (6 liters) per flush. In 1995 the National Energy Policy Act (H.R. 776) went into effect and mandated 1.6-gallon toilets for the entire U.S. Thus, new toilets must flush only 1.6 gallons (6 liters) of water, less than half the amount they used in the '80s. This limitation has now been extended to include commercial toilets as well as residential toilets.
In an effort to meet these requirements and to conserve water, there has been a trend toward toilet bowl designs that achieve adequate flushing while minimizing the use of water. However, as less and less water was available, efforts have shifted to complete redesign of the toilet. There have been two basic approaches: the gravity-flush siphon toilet--water stored in a tank drains from the tank to force waste down the drain by a siphoning action--and the pressure-assisted toilet. Toilets that pressurize the flush water generally perform better than conventional gravity-flush models but are noisier and usually more expensive. One example of a jet flush water supply system for a toilet stool is disclosed in U.S. Pat. No. 5,502,845 to Hayashi et al. This patent discloses a flush toilet stool that includes a toilet bowl and a trap drainage passage connected to the toilet bowl. The toilet bowl has a water jet hole defined in a bottom region thereof and opening toward the trap drainage passage. A water pump or similar pressurizing unit is coupled to the water jet hole for drawing water under lower pressure directly from an external water supply and expelling the water under higher pressure through the water jet hole toward the trap drainage passage to develop a siphon flow to discharge sewage from the toilet bowl through the trap drainage passage.
The problem with power-assisted toilets is that they are complex, expensive and loud. As a result, such assemblies do not find favor of consumers and are often difficult if not impossible for homeowners to repair.
Other attempts to use mechanical assistance for the flushing action suffer similar drawbacks. Briggs Industries, Inc. has, for example, introduced a pressure-assisted toilet that uses a new design configuration for both the tank and bowl. This newly designed system, called the Vacuity, creates a vacuum that further assists the flushing action of the toilet. This toilet is said to feature a larger water surface area in the bowl with a more efficient flush, plus the flush is a much less noisy than other pressure-assisted low-flow toilets on the market and perhaps less noisy than an old-fashioned conventional gravity-flush toilet. Again, however, this product is complex and its performance is not believed to be adequate.
For these reasons, low-flow toilets are still not well-accepted by many consumers, notwithstanding improvements in design and operation. Achieving an adequate flush with such limited use of water has proved to be a great challenge.
Thus, there remains a need for an improved flush-type toilet bowl of the type that discharges sewage by a siphoning action that is more simple, less expensive, provides better performance and is more silent than know high-performance toilets. There are, of course, a wide variety of siphon-type toilet stool constructions known. A typical siphon-type toilet is described in JP-U Sho-58-25381. The flush toilet bowl described in this publication is called the siphon jet type, and the water discharge trap of the toilet bowl has a stepped part in a descending path and is transversely bent substantially at a right angle on the downstream side of the stepped part and, thereafter, a discharge opening opens vertically (hereinafter, such a discharge trap is referred to as cross-laid type trap).
In this type of flush toilet bowl, the stepped part provided in the descending channel of the discharge trap causes a disturbance of water flow and forms the wall of water (seal), thereby producing a siphoning action, according to the principle of siphoning action. More specifically, before flushing, the interior of the discharge trap is under an atmospheric pressure which is the same as that on the surface of the gathered water. The supplying of flushing water to this place causes the disturbance of water flow due to the stepped part, thereby forming a wall of water (seal) which closes one end of the trap.
When the supply of water continues in a condition of the seal being formed, air within the trap is discharged together with water and the pressure within the trap becomes negative with respect to the atmospheric pressure. This negative pressure causes a drawing force. As the discharge of air further proceeds, the trap is substantially filled with water and, at this time, the maximum drawing force occurs. In particular, the siphoning action produced by the initial seal, grows by the discharge of air and puts forth the maximum drawing force when the trap is filled with water. Thus, it is recognized that the rapid production and growth of the siphoning action is important in order to save the amount of the flushing water.
Particularly, in the case where the position of the flush tank in the flush toilet bowl is attempted to be lowered for low-silhouetting the bowl, the potential energy of flushing water naturally becomes smaller, and so, in order to save an amount of flushing water, the realization of the above-described rapid production and growth of the siphon is all the more important and, moreover, ensuring a high capacity of water discharge is required.
U.S. Pat. No. 5,142,712 discloses a toilet bowl having a construction that causes air within the discharge trap to be discharged early to ensure the early production of the siphon. The toilet bowl is provided with a cross-laid type discharge trap in a similar way to the toilet bowl disclosed in the above-described JP-IT 58-25381. The crosslaid channel is bent upwardly before the discharge opening to provide a gathered water part before the discharge opening, in which a seal part is constituted. The air existing between the sealed water part and the above described gathered water part is drawn under a negative pressure produced within the sealed tank by the discharge of the water within the sealed tank, so that the air within the trap is discharged, thereby ensuring the early production of the siphoning action. In this connection, the reason why a ventilation space is provided in the gathered water part in such a toilet bowl, is that there occurs the following disadvantage: if there is no ventilation room, siphoning occurs very easily because of the seal being always constituted at two points. For example, in the case where a negative pressure occurs in the discharge pipe, such negative pressure sucks and discharges not only the water in the gathered water part, but also the sealed water per se in the toilet bowl, so that odor from the discharge pipe reversely flows into the chamber by way of the bowl part of the toilet bowl.
However, the toilet bowl described in said U.S. Pat. No. 5,142,712 requires a sealed tank construction because of the utilization of the negative pressure within the tank. Further, connection of the downstream of the sealed the interior of the tank produces the possibility of odor flowing into the tank, and so a separate construction on for preventing such a possibility is required.
Accordingly, as to the construction of a toilet bowl, it is believed that the toilet bowl disclosed in U.S. Pat. No. 5,142,712 is conventionally used in combination with an ordinary tank which has no sealed construction and has only a function of gathering and discharging water; however, there occur problems as described below.
Since the sealed part is constituted only by the gathered water part, a large amount of water is required to close the above-described ventilation room, and it takes much time to produce a siphoning action; consequently, a large amount of flushing water is required. Making this ventilation room narrower is considered, however, there is a problem in that if it is made too narrow, the above described disadvantages are apt to occur.
Further, an air pool is apt to occur in the inner portion of the descending channel of the trap and hinders the growth of a siphoning action, so, it is difficult to expect a sufficient effect in terms of the early production of a siphoning action in spite of the adoption of the sealed construction due to the gathered water part.
Moreover, since the weir between the rising channel of the discharge trap and the descending channel of the discharge trap is bent substantially at a right angle, the water which has passed through the weir comes off the weir and collides with the side wall at the back of the descending channel of the trap before it reaches the gathered water part, thereby forming water turbulence which swallows up the air within the trap. Further, it takes much time to discharge the air within the trap.
In addition, there was a problem in that in the crosslaid type of trap, water stream changes from the transverse direction to the vertical direction before the discharge opening in view of its construction; however, a change of direction of the water stream at this portion is not smoothly performed and a force of water discharge from the discharge opening is reduced.
Further, it is empirically known that the thinner the diameter of the discharge trap is, the earlier the production of the siphoning action is, however, if the diameter of the trap is made too thin, clogging of sewage is apt to occur and the primary function of the toilet bowl is adversely affected. Moreover, a large change in the diameter of the discharge trap causes a large loss of energy, so, when the siphoning action is produced, a force of suction due to the siphoning action does not become great, and an increase in the flushing capacity cannot be so expected.
In regard to another type of flush toilet bowl, a low-silhouette type of flush toilet bowl having a flush tank, in which flushing water is stored, disposed in a position lower than the toilet bowl body, is generally regarded as a high grade flush toilet bowl. Such a type of flush toilet bowl in the past includes the one which is described in JP-A Sho-64-75740. The toilet bowl described in this publication is a toilet bowl of a so-called siphon vortex type in which a siphoning action and a vertical action are used in combination. A decrease in the force of water supplied to the tank due to the fact that the position of the top of the flush tank B is lowered, as shown in FIG. 27, to suppress the water level of the flushing water from a rim surface 3a of the toilet bowl body A in a lower level, is supplemented in such a way that the flush tank B is positioned lower than the rim surface 3a to thereby increase the capacity of the tank to make an amount of water used at the time of flushing larger; thereby ensuring a total amount of discharge of 16 liters or so (total amount discharged from the toilet bowl to the discharge pipe in a single usage).
As noted above, however, the requirement of water saving for the flush toilet bowl has become very strict, especially, in the U.S. The total amount of discharge is now limited to 1.6 gallons (6 liters). Therefore, it is difficult to save water while ensuring the flushing capacity using the siphon-type toilet bowl having a conventional construction, and it is particularly difficult to cope with such a requirement with the low-silhouette type toilet bowl.
The present invention has been made taking the above described problems in the prior art into consideration and aims at providing a flush toilet bowl which can sufficiently cope with the strict requirements of water saving in recent years and allows sufficient flushing capacity to be displayed.